1. Field of the Invention
The present invention relates to a device having magnetometers and more specifically to a fluxgate. The invention also relates to a method for manufacturing such a fluxgate.
2. Brief Description of the Related Art
A fluxgate is a device for measuring the Earth's magnetic field, making it possible to determine the orientation of the Earth's magnetic field with respect to a reference axis.
When the fluxgate is mounted on an aircraft, the reference axis is aligned with the axis of movement of the aircraft, such that the fluxgate makes it possible to determine the aircraft's magnetic heading.
A fluxgate comprises two uniaxial magnetometers arranged perpendicular to one another in a substantially horizontal plane.
Every magnetometer comprises a core made of a material with high magnetic permeability, chosen such that the Earth's magnetic field is enough to bring the core into a state close to its saturation state. The cores are surrounded by a primary winding and a secondary winding. The primary winding is supplied by an alternating current in order to give rise, in the core, to a variation in the magnetic field which in turn produces a potential difference across the terminals of the secondary winding. Processing the signal which appears on the secondary winding makes it possible to determine very precisely the magnetic field component in the direction of the windings in question.
In order to isolate the magnetometers from the vertical component of the Earth's magnetic field, they must be held in a plane which is as horizontal as possible. To that end, the cores are mounted on a pendulum which is suspended below a plate. The pendulum is enclosed in a casing which is attached to the plate and which is filled with a liquid having a viscosity which is high enough to damp the movements of the pendulum.
This means that known fluxgates are relatively heavy and bulky.
Furthermore, a drop in temperature leads to an increase in the viscosity of the liquid, eventually preventing the pendulum from swinging. Thus, these fluxgates cannot be used below a certain temperature, specifically −2° C. for the most high performance ones. However, certain aircraft flying at high altitude, frequently experience such temperatures.
Documents FR 2 238 162 and FR 2 099925 describe such fluxgates.